In the past apparatus for heating and/or cooling molds onto which thermoplastic material is deposited and fused to form a thin shell have utilized a tube bundle fixed between a plenum inlet and a plenum outlet so as to direct a jet stream of fluid against the mold for treating the thermoplastic material deposited therein. Such systems, while suitable for their intended purpose, were configured such that each time a different mold was placed on the apparatus, it was necessary to provide a different plenum arrangement that would both accommodate the different mold and support a different tube bundle configured to direct a different jet stream pattern against the mold for balancing the heat pattern across the mold for assuring that the mold part being produced would be evenly formed across the heated mold surface on which the thermoplastic material is deposited and fused to form a thin shell part on the mold. Examples of such prior art arrangements are shown in U.S. Pat. Nos. 4,621,995; 4,623,503; and 5,106,285.
Since the mold cavity positions are established by the fixed tubing on the mold box, molds with different shapes and dimensions cannot be substituted for a mold that conforms to the length and position of the tubes that comprise the tubing. As a consequence, the production flexibility of mold boxes with a fixed tube sheet are greatly limited, e.g., to the use of molds having a shape that conforms to the fixed tubing sheet in the mold box.